1. Preheat your oven to 250°C (480°F). Grease a 30x40 cm (12x16 inch) baking dish and line with parchment paper.

2. In a bowl, mix the flour, 100 g (1/2 cup) of the confectioners' sugar, and baking powder. Add the cold butter and work into a crumbly dough using your fingers or a pastry cutter.

3. Press 2/3 of the dough evenly into the prepared baking dish. Set aside the remaining dough for the topping.

4. In another bowl, mix the almond paste, remaining 100 g (1/2 cup) confectioners' sugar, vanilla extract, and a pinch of salt until smooth.

5. Spread the almond mixture evenly over the base. Add a layer of vanilla custard on top.

6. Crumble the remaining dough over the custard layer.

7. Bake in the preheated oven for about 30 minutes or until golden brown and a skewer inserted into the center comes out mostly clean with a few moist crumbs.

8. Allow the cake to cool completely in the pan set on a wire rack.

9. Dust with additional confectioners' sugar. Using a sharp knife, cut into squares and serve. Enjoy!